1. Technical Field
The present invention relates generally to contact and non-contact inspection of a workpiece and, in particular, to measuring a surface geometry of a workpiece relative to a common measurement coordinate system.
2. Background Information
Various qualification methods are known for determining whether, for example, a rotor blade casting die forms a rotor blade that complies with a blade design specification. The blade design specification may include information regarding geometry and/or structural properties of the rotor blade.
A typical qualification method for a rotor blade casting die includes creating a surface geometry map of a rotor blade, formed by the die, with a plurality of inspection devices. Different inspection devices are typically utilized for the purposes of redundancy. A first surface geometry map may be created, for example, with a non-contact inspection device, and a second surface geometry map may be created with a contact inspection device. Measurement data from the first and second surface geometry maps may be respectively analyzed to determine whether measured dimensions of the rotor blade are within tolerance of the geometry designated in the blade design specification. The measurement data may be difficult to analyze, however, because each inspection device may utilize its own local coordinate system during the mappings. The measurement data from the first and second surface geometry maps therefore generally must be individually best fit to the geometry designated in the blade design specification before the tolerances are evaluated, which may introduce additional coordinate system alignment error into the evaluation.